1. Field of the Invention
The present invention relates to a hinge, and more particularly to a hinge for smoothly opening or closing a foldable electronic device.
2. The Related Art
As the development of modern mobile communication industry, portable electronic devices such as cellular phones, notebook computers and personal digital assistants, etc., become more and more popular. Thereinto, many portable electronic devices have a function of displaying image. In order to display image as distinctly as possible, so screens of the portable electronic devices need to be designed as big as possible. But it is not convenient to carry the portable electronic device with a big screen. That is, the required big screen and the required small size of the portable electronic device are contrary. To solve the problem, foldable electronic devices have been developed. Generally, the foldable electronic device has a cover which is usually used as a screen of the foldable electronic device, and a main body which is joined together with the cover by some type of hinge allowing the cover to be unfolded from the main body.
Referring to FIG. 1, a conventional hinge used in a foldable electronic device which has a cover and a main body is represented. The hinge includes a cylindrical shaft 200 passing through a rotatable cam 600 and a sliding cam 500. The rotatable cam 600 protrudes downward to form two pushing portions 601 at bilateral sides thereof. The sliding cam 500 defines two concave grooves 501 receiving the pushing portions 601 respectively. A spring 400 encircles the shaft 200. One end of the spring 400 is fixed on the sliding cam 500, and an opposite end of the spring 400 is mounted on a cap 100 which plugs an end of a housing 300. The spring 400 and the sliding cam 500 are slideably received in the housing 300. If the foldable electronic device needs opening, a user firstly unfolds the cover from the main body of the foldable electronic device at an angle. The force that the user provides pushes the pushing portions 601 to the top of the concave grooves 501. At the same time, the sliding cam 500 is compelled to slide toward the end of the housing 300, and the spring 400 is compressed. Then, the user stops acting on the foldable electronic device, and the elastic force of the spring 400 drives the foldable electronic device opened fully.
However, the process that the compressed spring 400 drives the foldable electronic device opened fully is too quickly. Therefore, an impact is produced between the cover and the main body, so the foldable electronic device is easy to be broken or damaged. Thus, a highly reliable hinge is desired to overcome the disadvantage mentioned above.